A sharp decline in bond yields last week also fueled the wave of selling.

China, the world's second-largest economy after the United States, is weakening. And other economies that depend heavily on purchases in China have suffered as a result.

On Monday, another survey showed that business economists foresee a significant slowdown in U.S. growth over the next two years. That's in sharp contrast to the Trump administration's predictions that growth will accelerate in the coming years.

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The market's recent skid follows what has been a strong start to the year on Wall Street as stocks rebounded from a steep slide at the end of 2018. The bull market for U.S. stocks recently marked its 10th anniversary and is now the longest of all time.

Monday's shaky start to the week for markets came amid a lull in news on the tariffs war between the United States and China. Trade talks are due to resume Thursday in Beijing.

Despite the market's recent slide, the S&P 500 index is still up more than 11 percent so far in 2019, which is still an unusually strong start to a year.

ECONOMIC JITTERS: Citing a global slowdown and trade conflicts, economists from the National Association for Business Economics collectively project that growth will reach a modest 2.4 this year and just 2 percent in 2020. Still, the economists say they think a recession remains unlikely any time soon.

Worried investors have shifted money into bonds, sending yields lower. The yield on the 10-year Treasury slid to 2.42 percent from 2.45 percent late Friday.

That remains below the yield on the three-month Treasury bill, currently 2.45 percent, a worrying sign that in the past has preceded recessions. That "inversion" occurred on Friday and has spooked investors.

BLACKOUT AVERTED: Media company Viacom rose 5.1 percent after the company reached a carriage deal with AT&T that would avert a blackout of its channels including Comedy Central and MTV to AT&T customers.

DOWNGRADED: Akamai Technologies slid 5.1 percent after analysts at Deutsche Bank downgraded the stock to "Sell" from "Hold," citing expectations that sales and earnings will fall short Wall Street forecasts through fiscal 2021.

OVERSEAS: Major European stock indexes headed lower as uncertainty over Brexit continued. British Prime Minister Theresa May was under intense pressure to resign as the price of breaking the country's Brexit impasse and winning support for her unpopular EU divorce deal.